Drum suspension



Jan. 4, 1955 1. L. LANGVAND ET AL 2,693,510

DRUM SUSPENSION 2 Sheets-Sheet 1 Filed Dec. 14, 1946 s RMM O dmo NVQO Eg r mac ZJs

GE m 444, ATTORNEY United States Patent "Ofiice DRUM SUSPENSION @12 L, Langigand -tfilen' J. Schoessow,- rand :E.m.est

.1 Brooks-t liarbertou, :Qhio, assignors to The Babcock .&

; Wilcox Company,=.-Rocklei gh,-..N. 1., a corporation .of

New Jersey :Application December'l l 1946,. Serial No. 716,270

*Claims. j (Cl. 122-3510) The invention herein disclosedrelates to the'suspension --;of:.a.p ressure vessel subject to thermal expansion during --'oper.at1on,; amore-specific application of the invention s'be ing-to%1he:.suspensionof-.a horizontally disposed cylindrical: drum associated-. with a boiler or other heat-transfer zrapparatus.

Heretotore, in the-suspensionof a boiler drum from an ..overheadstationaryzstructure,"ithas been customary to :-.employ a pair of 'drum straps-in the form ofuU-bolts' engaging the lower half. of the drum adjacent opposite ends, each .U-bolt :being .formed of a continuous length of steel rod .of circular cross-section and being supnported byzits threaded-upper ends on washer members designed :to :permit limited-angular movement of the strap in accordance'withthe longitudinal drum movewment caused-by-:temperaturechanges. For boilers of :small and mediumrcapacities-such a means of support has been found entirely satisfactory.

In large capacity 'boiler units, the major portion of the ewei'ght -is'=supported from thextop and includes not only -weight-' of'the boiler structure but alsoweight of the furnace structure. In such units, certain'parts associated .-with .either'theboiler orfurnace structure, or both, are connected to the drum and are'supported thereby, so that supports for the drummust-sustain a total weight in ex- .cess of-the-weight of the drum itself. The total-drum 'load-tobe suspendedalso increases with-the pressure at :Which'theboiler is designed to be operated'due to the greater. wall thicknesses required-for the drum and assodated-suspended pressure parts. Itfollows thereforethat :as .aprimary requirement the drum suspension members 'musthave relatively-large cross-sectional areas-to provide -=adequate .tensilestreng'th-for support of the total'drum load involved.

In modern central :stationboilers of increasingly higher capacities and pressurespthe'main steam and water drums may have diameters ranging upwardly to about 6-feet and lengths upwardlyof '40 feet, involving drum-loads ranging, for example, between 1,000,000 and 2,000,000 pounds. In'theusual boiler construction an upper boiler drum can be supported only adjacent itsends exteriorly opposite upright walls of'the setting, thereby determining the areas of support or suspension at widely separated-locations, such as 40 feet or more apart measured longiwtudinally of the'drum. .When the boiler .is-placed in operation and 2 the drum :brought up 1 to. saturation atempera- -t ure, :thermaLelongation-of-the drum-causes the two drum "support areas to become more" widely separated-and :the lower :ends of the suspensiongmembers-torbemoved-apart acorrespondingdistance, in some instances; the drum elongation being-about-two inches, -with the drumengaging -end-of-eachmembermoving outwardly a distance of about one inch. Such movement of each suspension-member .adiacent,the drum :is, of-course, 'greaterat the.higher-op- .--.e ra .ting pressures-zduc toiithehigher saturation temperatures;and.-rnust,be provided for. byidefiection in the rn emr itself, .or;by,.-some special supportarrangement, .since thesteel supporting structure ,-to=whi'ch the member :isattachedpremains at a considerably :lower temperature. -Specialsupport arrangements have been proposed whereby suchmovements of the suspension members are-per- :rnitted without-stress inducing deflections therein but .such 'devices are of complicated construction and expensive dueto the high bearingloadsaandhigh .shearing forces .involved.

whendrumtstraps, of the-,circulansection..U=bolt type are employed for large high pressure drums ancl .correv Fatented Jan. 4, 1955 .2 spondingly.heavy=drum-loads, the requirements involve a steelsrod oflarge cross-section to withstand the direct utension--loadinvolved, and a rod also of suificient length .-to permit the necessary amount of deflection due to drum 5 --selongation:without'exceeding a predetermined maximum :xtotalworking stress of 15,000 p. s. i., for example, inclusive of direct tension and bending stresses, the rod being considered; as axcantilcver fixed at-the drum and free at :its uppertrocker-supported ends. Solid steel rods of large l0 "diameters-may lack the requireduniformity of metal- ..=lurgical quality. The use of large circular section rods "may: also involve lengths which are considerably greater 'ithan thei height available ordesired between the drum andj-theoverhead drum supporting structure. Limita- 1sjftioncofdrum strap.length is therefore an important con- 1-.s,idcration-in;its effect on overall boiler height for any given: boiler construction.

..'-'An object of our invention therefore contemplates an zcimprovedr-formr-of :drumsuspension permitting the drum ."to:be=-positioned closely adjacent its overhead stationary 'F-SXPPQX'iiilfld'thClCbY in boiler construction contributing to a reduction in overall boiler height.

. 'Anot-herobject of-the invention is to provide a drum :-suspension in-which the total load. is divided between ele- 'mensof'relatively small cross-section adjacent each end of thedrum.

- An additional object is to provide drum suspension ele- -ments off-predetermined uniformly high quality throughout their cross-section.

A further object is to provide a drum suspension unit :comprising a group of suspension elements of which each :hasits-minimum moment of inertia about an axis normal to longitudinal movement of the drum.

A; more specific object is to provide a multiple plate suspension unit of generally U-shaped formation in which sliding-,andfriction between plates is maintained at a minimum.

Thevarious features of novelty which characterize our invention are pointed out with particularity in the claims annexed to-and forming a part of this specification. For

a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described a preferred-embodiment of our invention.

Of-the'drawings: Fig. 1 is an-elevational view featuring an improved form of drum strap as an embodiment of our invention; Fig. 2 is a side view of the structure illustrated in Fig. 1; d,

' Figs. 3,4 and 5 are enlarged vertical sections of Fig. 1 takenalong lines 3-3, 4-4, and 55, respectively.

Figs. 1 and 2 illustrate an embodiment of our invention "as-applied .for example to the suspension of a cylindrical 55..steam-and-water drum 12 which for the purpose of this aapplicationmay be taken as the principal supported elen1ent'in-a highv capacity high pressure vapor generating .-..unit of the construction disclosed-in the copending appli- Hcation-pf-Arthur E. Raynor, Serial No. 638,941, filed Jan- -.uary. 4, 19.46,: and since issued as U. S. Patent 2,512,677,

.dated June 27, 1950. The drum 12 is suspended by means ..'of;dr .um.:straps; 14, ofvwhich one only is shown, from an ,overheadsupporting frame structure which includes horitzontally extending .beammembers 16 and 18 having their pfpper flange surfaces in a common horizontal plane 19,

.t etwo d r,um straps 14 engaging the drum 12 adjacent opposite ends at locationsexteriorly of opposite side walls of'the boiler'setting as indicated more particularly in the aforesaid application,- the outer surface of one such wall being-indicated'by line 21 in Fig. 2 of the present application, the adjacent 'drumend thus being'toward the left of walbfil=as viewed in this figure.

Eachdrum strap'14 is of multiple plate construction providing a suspension unit of generally U-shaped formation,:;as-seen :inFig. l, the lower loop portion or drum saddle section 23-of'the strap embracing substantially the;entire lower half of. drum 12, and the upright leg tportions or-sections 24 extending upwardly to an eleva- -.tion-above the short length .Lbeam-members-ZS which are 30 securedIby .welds.26 to .the horizontally spaced I-beam members 16 and '18, or other adjacent portionsofgthe main supporting frame, each I-bearn member 25 being reinforced by plates 27 which are secured thereto by welds 28. Each leg of strap 14 terminates in a transverse upper end portion or section 29 by which drum load is transferred through I-beam members 25 to the main supporting structure, each terminal portion 29 being seated on wedges 31 inserted between portion 29 and the beam members 25 for the purpose of adjustment as hereinafter described, and the wedges maintained in final position relative to supports 25, for example, by welds 32.

The lower loop portion 23 of each strap 14 comprises a group of horizontally spaced arcuately formed saddle plates 34 arranged in edgewise relation with respect to drum 12 and assembled with filler plates or spacers 35 therebetween which are secured to adjacent plates 34 by welds 36, the inner arcuate edge of each plate 34 having recesses or relieved areas 37 therein at intervals to provide arc-uately spaced drum engaging portions 38 which when the plates 34 are assembled are machined to the measured radius of the outer wall of the drum, the provision of recesses 37 resulting in a closer proximity of fit with the drum and a more uniform loading of each saddle plate 34. The plates 34 terminate in horizontal upper edges 39 at substantially the level of the horizontal central axis of drum 12.

The vertically disposed leg portion 24 of each strap 14 comprises a group of relatively narrow fiat hanger bars or plates 41 of rectangular cross-section interleaved in pairs at their lower ends with the spaced upper ends of saddle plates 34 to which plates 41 are connected by two rows of round bars or pins 42 having threaded ends to receive the holding nuts 43 which are suitably tacked welded thereto, a rectangular washer 45 being inserted between each nut 43 and an outer saddle plate 34. The spacing of the pairs of hanger plates 41 in each leg of the strap is maintained by means of pipe spacers 46, at one or more elevations, through which bolts 47 are inserted and the entire group of plates 41 tied together against the spacers by means of nuts 48, a washer 49 being suitably inserted between each bolt head and nut and the adjacent outer plate 41. The plates '41 are thus maintained at substantially equal spacings throughout their lengths and, due to clearances provided'around bolts 47 through the plates and pipe spacers, provide a unitary structure having high tension load characteristics without unduly increasing the resistance of the assembly to deflection, each plate 41 being free to move relative to an adjacent plate to a limited extent and thereby function ing more nearly as an individual plate, in so far as deflection is concerned, than if incorporated in a totally rigid assembly. Each plate 41, in cross-section, is of smaller dimension longitudinally of the drum than in a direction normal thereto, thereby providing its minimum moment of inertia about an axis normal to the plane of its deflection, that is, a vertical plane parallel to the longitudinal axis of the drum.

The transverse upper end section or cross piece 29 in which each drum strap 14 terminates comprises spaced plates 51 interleaved with the upper ends of the hereinbefore mentioned pairs of hanger plates 41, each set of cross piece plates 51 and hanger plates 41 being held together in assembled pivotal relation by a pin 52 having threaded ends to receive the holding nuts 53 which are suitably tack welded thereto, a rectangular washer 54 being inserted between each nut 53 and the adjacent outer cross piece plate 51. In the form shown, where three pairs of plates 41 are employed in each leg 24 of the strap, the plates forming the central pair terminate above the cross piece 29 in an upwardly extending portion 56 having a hole 57 therein mainly for purposes of erection, whereby a strap 29 may be lifted into and held in position prior to and during assembly of the cross piece plates 51, and duringadjustment and welding of wedges 31, there being a separate pair of oppositely inclined wedges 31 cooperating with the inclined lower edges 58 of each cross plate 51 so as to afford independent adjustment of each such plate whereby accurate alignment of the holes in plates 41 and 51 may be attained for the reception of pins 52, and vertical adjustment of drum position efiected,

the plates 51 thereafter being maintained in alignment by means of bars 59 extending across opposite ends of each group of plates 51 and each welded to all plates of a group.

In the construction of drum strap described, full advantage is taken of the elastic properties of the metal of which the plates are formed. In addition to the loading of the strap plates 41 in direct tension, there is a bending stress to be accommodated as a result of the deflections accompanying variations in drum length in response to temperature changes. However, the hanger plates 41 are relatively thin in the direction of drum movement and thus are capable of being deflected to the extent required without causing any considerable increase in total working stress due to bending, each plate having for example a thickness of three-eights to three-quarters of an inch and a width of approximately twenty to thirty times the thickness. The total working stress, inclusive of stresses in direct tension and bending, is therefore maintained well within permissible limits for the metal involved. The small addition of stress due to bending enables shorter straps to be employed so that a considerable reduction in height of the supporting steel structure may be effected and a more economical boiler installation provided. Apart from an economical standpoint, there drum are occasions when a limited available height is a controlling factor in the design of boiler that can be installed in which cases employment of the present disclosed form of suspension is especially beneficial.

The provision of a laminated structure as shown, utilizing a plurality of plates throughout, is also advantageous in that at each connection between sections the total shearing force is subdivided and thus applied in correspondingly smaller units at a greater number of locations, thereby permitting the use of connecting pins of relatively small cross sectional areas.- The pins of reduced cross section are also suitable as regards resistance to bending because of the plurality of points of support and the resulting short span between these points of support. In the connection between the saddle plate section 23 and each upright leg section 24, where a plurality of pins 42 are utilized, the shearing forces are further distributed and the required cross sectional area of each pin correspondingly reduced.

In addition to the deflection of strap plates 41 in the direction of drum movement there is also a certain amount of radial movement which takes place due to radial expansion of the saddle plates 34 so that the resultant movement of the strap plates deviates slightly from normal with respect to the plane of the plates and ends to produce a slight twist in the plates. However, this radial component of plate movement is relatively small considering the extent of axial movement involved. Any increase in bending stress due to the twist is thus maintained at a low value and is no detriment to operation for the extent of drum length variations normally encountered.

While in accordance with the provisions of the statutes we have illustrated and described herein the best form of our invention now known to us, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by our claims, and that certain features of our invention may sometimes be used to advantage without "a corresponding use of other features.

We claim:

1. In heat transfer apparatus, a horizontally axised cylindrical drum subject to variations in its axial length as a result of thermal expansion and contraction, a suspension for said drum comprising a drum supporting saddle section embracing the lowermost surface portion of said drum, a pair of upright hanger sections having lower end portions rigidly connected to transversely spaced portions of said saddle section, and means pivotally connected to upper end portions of each of said hanger sections for transferring suspended drum weight to an overhead load supporting structure, said saddle. section and said hanger sections each comprising longitudinally spaced plates interleaved with and connected to plates of the respective other sections, each of said plates of said hanger sections having its upright facing surfaces substantially normal to the longitudinal axis of said drum, each of said saddle plates presenting a concave upper edge portion toward .said drum and providing therewith mutually contacting surfaces of substantially common curvature about the longitudinal axis of said drum, one of said last named surfaces being formed with arcuately spaced recesses therein to reduce the area of saddle plate engagement with said 2. Apparatus for suspending a horizontally elongated drum comprising a rigidly formed drum saddle section adapted to extend transversely of said drum to positions at opposite sides of said drum, a pair of vertically disposed hanger plate sections arranged substantially in a common plane at opposite ends of said saddle section and each adapted to flex in a direction normal to said plane, means rigidly connecting the lower ends of each of said hanger plate sections to said opposite ends of said saddle section, and means pivotally connected to upper ends of each of said hanger plate sections for transferring suspended weight to a load supporting structure, said hanger plate sections respectively comprising a plurality of plates each of substantially lesser thickness than Width in directions respectively transverse and parallel to said plane.

3. Apparatus for suspending a horizontally axised cylindrical drum which during operation is subject to thermal expansion, said apparatus comprising a rigidly formed drum saddle section having an arcuately formed upper surface portion adapted to engage a similarly formed lower surface portion of said drum, a pair of vertically extending flexible hanger sections arranged in horizontally spaced relation throughout and having lower end portions rigidly connected longitudinally of said drum to horizontally separated portions of said saddle section, and means separately connected in pivotal relation to upper end portions of each of said hanger sections for transferring suspended drum weight to a load supporting structure, each of said hanger sections being formed of relatively thin plates of substantially lesser thickness than width in directions respectively parallel and transverse to the longitudinal axis of the drum to be supported and of substantially greater vertical length than the horizontal distance separating said hanger sections.

4. Apparatus for suspending a cylindrical drum which has its longitudinal axis horizontally disposed and which during operation is subject to variations in length as a result of thermal expansion, said apparatus comprising a saddle section of rigid formation having a concave upper drum seat portion adapted to engage a lower arcuate portion of the drum to be suspended, a pair of upright hanger sections arranged in horizontally spaced relation throughout in a direction transverse to said axis, means rigidly connecting longitudinally of said drum the lower end portions of said hanger sections to horizontally opposite upper end portions of said saddle section, and means pivotally connected to upper end portions of said hanger sections for transferring suspended drum weight to a stationary support, each of said hanger sections being formed of relatively thin plates arranged transversely of said axis and extending vertically in lengths substantially greater than the horizontal distance separating said hanger sections so as to render said plates flexible in the direction of said drum length variations, said plates of each of said hanger sections being arranged in groups spaced apart in a direction parallel to said axis and interconnected at intervals throughout the height of said hanger sections.

5. Drum suspension apparatus as claimed in claim 4 wherein individual hanger section plates have an average width dimension transversely of said axis of the order of at least twenty times an average thickness dimension longitudinally of said axis so as to resist flexing in a direction transverse to the length of the drum.

References Cited in the file of this patent UNITED STATES PATENTS 486,804 Wood Nov. 22, 1892 808,848 Killam Jan. 2, 1906 892,105 White .June 30, 1908 1,193,480 ODay Aug. 1, 1916 1,645,762 Lohbiller Oct. 18, 1927 1,852,683 Sunderland Apr. 5, 1932 1,890,886 Rather Dec. 13, 1932 1,977,247 Scott et al Oct. 16, 1934 2,016,787 Liessenberg Oct. 8, 1935 2,416,058 Mangnall Feb. 18, 1947 FOREIGN PATENTS 597,949 France of 1925 402,145 Great Britain of 1933 

